<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    img{
        width: 300px;
        height: 300px;
    }
</style>
<body>
    <div id="app">
        <img :src="arrs" alt="">
        <ul>
            <li v-for="(item,index) in arr" @click ="arrs = item">{{index+1}}</li>
        </ul>
    </div>
    <script src="../Dev-tools/vue.js"></script>
    <script>
        new Vue({
            el: "#app",
            data: {
                arr: [
                    "img/1.jpg",
                    "img/2.jpg",
                    "img/3.jpg"
                ],
                arrs: "img/2.jpg"
            }
        })
    </script>
</body>

</html>